This application is concerned with advancing the scientific experience and development of the candidate while developing a comprehensive understanding of the cryobiology of felid sperm. The ultimate research aim is to improve the efficiency of assisted reproduction, specifically artificial insemination (AI), for propagating cats valuable to biomedical research and for conserving endangered felids. Domesticated cat models for human disease and endangered felid species frequently experience poor reproductive success, physical or behavioral incompatibilities, and abnormal sperm traits. AI with cryopreserved sperm could circumvent these problems. However, lack of knowledge about the cryobiology for felid sperm has hindered effective use of these powerful tools. This application describes basic and applied studies involving domestic cat populations that experience normospermia (>60% morphologically normal sperm) or teratospermia (<40% normal sperm), a condition commonly observed in rare felids. Findings also will be compared to wild felids that are normospermic (leopard cat), or teratospermic (clouded leopard) nondomestic felids. Comparative studies will focus on the impact of cryoprotectant and temperature on cat sperm physiology and function, specifically: 1) physical and biomedical properties of sperm plasma membranes pertaining to cryodamage sensitivity; 2) stabilization of sperm function; and 3) identification of cryopreservation conditions that maximize sperm function. Studies will identify variables most influential to post-thaw sperm survival, allowing an optimal laboratory protocol to be developed and tested across cat populations and species. The best method will be used systematically for AI in partnership with institutions holding the rarest cats of value to biomedical research and a host of selected endangered species. This training/research approach will allow the candidate career advancement as a reproductive specialist in laboratory and rare felid species. Extensive interactions with eight investigators at seven institutions will provide access to fundamental research concepts of cell biology and sophisticated techniques, including membrane lipidology, cell volume measurements, flow cytometry, cryomicroscopy and AI. Finally, the research will determine the factors influencing cryosurvival of felid sperm while identifying sperm cryobank protocols that will lead to more efficient and effective propagation and conservation of rare felids.